[quote]ORIGINAL: AMB

Hobbsy The basic principle of Boyles Gas law is any gas (even air) expands as the temp increases less dense and the converse of course as it gets colder, gas can be compressed to a point where they become a liquid, CO2, freon, allowing a temendous amount to be stored and as released becomes a gas again. and cools this of course
follow an equation for temp and pressure for a more detailed and precise explanation go on wikipedia an look up Boyles law easy to understand martin